Blue Photoluminescence from Chemically Derived Graphene Oxide

Eda, Goki; Lin, Yi-Hsien; Mattevi, Cecilia; Yamaguchi, Hisato; Chen, Hsin‐An; Chen, I-Sheng; Chen, Chun-Wei; Chhowalla, Manish

doi:10.1002/adma.200901996

Cited by 1,865 publications

(1,663 citation statements)

References 39 publications

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“…Moreover, excessive etching leads to additional defects and an increase of oxygen to carbon ratio in GQDs, resulting in the collapse of the 10-nm-sized sp 2 carbon structure in GQDs. 30,37,38 Similar results can also be observed for larger GQDs ( Figure S4). Furthermore, we investigated the influence of substrate functionalization on the PL emission characteristics of GQDs.…”

supporting

confidence: 84%

“…A similar tendency also appeared for the GQDs fabricated by GO. 30,34 In both sets of results shown in Figures 3 and 4, it is recognized that oxygen defects can be formed on GQDs, which formation causes the variation of the Raman spectra and the PL emission. To prove the effect of oxygen at the surface of the GQDs, controlled oxidation and reduction were performed on the GQDs by air plasma and hydrazine ( Figure 5).…”

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confidence: 90%

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Uniform Graphene Quantum Dots Patterned from Self-Assembled Silica Nanodots

et al. 2012

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Graphene dots precisely controlled in size are interesting in nanoelectronics due to their quantum optical and electrical properties. However, most graphene quantum dot (GQD) research so far has been performed based on flaketype graphene reduced from graphene oxides. Consequently, it is extremely difficult to isolate the size effect of GQDs from the measured optical properties. Here, we report the sizecontrolled fabrication of uniform GQDs using self-assembled block copolymer (BCP) as an etch mask on graphene films grown by chemical vapor deposition (CVD). Electron microscope images show that as-prepared GQDs are composed of mono-or bilayer graphene with diameters of 10 and 20 nm, corresponding to the size of BCP nanospheres. In the measured photoluminescence (PL) spectra, the emission peak of the GQDs on the SiO 2 substrate is shown to be at ∼395 nm. The fabrication of GQDs was supported by the analysis of the Raman spectra and the observation of PL spectra after each fabrication step. Additionally, oxygen content in the GQDs is rationally controlled by additional air plasma treatment, which reveals the effect of oxygen content to the PL property.

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confidence: 84%

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confidence: 90%

Uniform Graphene Quantum Dots Patterned from Self-Assembled Silica Nanodots

et al. 2012

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“…In direct-bandgap semiconductors, the radiative recombination of electrons and holes produces photons, and occurs much more efficiently than in indirect-bandgap semiconductors. The direct bandgaps of monolayer semiconducting TMDCs make them ideal candidates for the active light-emitting layer in future flexible optoelectronics, unlike graphene, which lacks a bandgap and requires chemical treatments to induce local bandgaps that photoluminesce 150,151 . Examples of electroluminescence in TMDCs include MoS 2 emitting light by electrical excitation through Au nano-contacts 152 , and electroluminescence from SnS 2 exfoliated from lithium intercalation and incorporated into a composite polymer matrix 56 .…”

Section: Optoelectronicsmentioning

confidence: 99%

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

et al. 2012

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699M any two-dimensional (2D) materials exist in bulk form as stacks of strongly bonded layers with weak interlayer attraction, allowing exfoliation into individual, atomically thin layers 1 . The form receiving the most attention today is graphene, the monolayer counterpart of graphite. The electronic band structure of graphene has a linear dispersion near the K point, and charge carriers can be described as massless Dirac fermions, providing scientists with an abundance of new physics 2,3 . Graphene is a unique example of an extremely thin electrical and thermal conductor 4 , with high carrier mobility 5 , and surprising molecular barrier properties 6,7 .Many other 2D materials are known, such as the TMDCs 8,9 , transition metal oxides including titania-and perovskite-based oxides 10,11 , and graphene analogues such as boron nitride (BN) 12,13 . In particular, TMDCs show a wide range of electronic, optical, mechanical, chemical and thermal properties that have been studied by researchers for decades 9,14,15 . There is at present a resurgence of scientific and engineering interest in TMDCs in their atomically thin 2D forms because of recent advances in sample preparation, optical detection, transfer and manipulation of 2D materials, and physical understanding of 2D materials learned from graphene.The 2D exfoliated versions of TMDCs offer properties that are complementary to yet distinct from those in graphene. Graphene displays an exceptionally high carrier mobility exceeding 10 6 cm 2 V -1 s -1 at 2 K (ref. 16) and exceeding 10 5 cm 2 V -1 s -1 at room temperature for devices encapsulated in BN dielectric layers 5 ; because pristine graphene lacks a bandgap, however, fieldeffect transistors (FETs) made from graphene cannot be effectively switched off and have low on/off switching ratios. Bandgaps can be engineered in graphene using nanostructuring [17][18][19] , chemical functionalization 20 and applying a high electric field to bilayer graphene 21 , but these methods add complexity and diminish mobility. In contrast, several 2D TMDCs possess sizable bandgaps around 1-2 eV (refs 9,14), promising interesting new FET and optoelectronic devices.TMDCs are a class of materials with the formula MX 2 , where M is a transition metal element from group IV (Ti, Zr, Hf and so on), group V (for instance V, Nb or Ta) or group VI (Mo, W and so on), and X is a chalcogen (S, Se or Te). These materials form layered structures of the form X-M-X, with the chalcogen atoms in two hexagonal planes separated by a plane of metal atoms, as shown in Fig. 1a. Adjacent layers are weakly held together to form the bulk crystal in a variety of polytypes, which vary in stacking orders and metal atom coordination, as shown in Fig. 1e. The overall symmetry of TMDCs is hexagonal or rhombohedral, and the metal atoms have octahedral or trigonal prismatic coordination. The electronic properties of TMDCs range from metallic to semiconducting, as summarized in Table 1. There are also TMDCs that exhibit exotic behaviours such as charge density waves ...

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“…Their photoluminescence characteristics are linked to the sizes and ratio of sp 2 and sp 3 domains. The mechanism is considered complex and involves 1) defects' state emission/surface energy traps and 2) intrinsic state emissions, which include electron–hole recombination, quantum size effects/zigzag states 170, 171, 172, 173, 174. The emission characteristics were linked to surface chemistry and thus to alterations in the bandgap 175.…”

Section: Applications Of the Photochemical Activity Of Nanoporous Carmentioning

confidence: 99%

Origin and Perspectives of the Photochemical Activity of Nanoporous Carbons

Bandosz

Ania

2018

Advanced Science

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Even though, owing to the complexity of nanoporous carbons' structure and chemistry, the origin of their photoactivity is not yet fully understood, the recent works addressed here clearly show the ability of these materials to absorb light and convert the photogenerated charge carriers into chemical reactions. In many aspects, nanoporous carbons are similar to graphene; their pores are built of distorted graphene layers and defects that arise from their amorphicity and reactivity. As in graphene, the photoactivity of nanoporous carbons is linked to their semiconducting, optical, and electronic properties, defined by the composition and structural defects in the distorted graphene layers that facilitate the exciton splitting and charge separation, minimizing surface recombination. The tight confinement in the nanopores is critical to avoid surface charge recombination and to obtain high photochemical quantum yields. The results obtained so far, although the field is still in its infancy, leave no doubts on the possibilities of applying photochemistry in the confined space of carbon pores in various strategic disciplines such as degradation of pollutants, solar water splitting, or CO2 mitigation. Perhaps the future of photovoltaics and smart‐self‐cleaning or photocorrosion coatings is in exploring the use of nanoporous carbons.

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Blue Photoluminescence from Chemically Derived Graphene Oxide

Cited by 1,865 publications

References 39 publications

Uniform Graphene Quantum Dots Patterned from Self-Assembled Silica Nanodots

Uniform Graphene Quantum Dots Patterned from Self-Assembled Silica Nanodots

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

Origin and Perspectives of the Photochemical Activity of Nanoporous Carbons

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